Gunpla Building Community

I recently completed my second Gunpla... still very new. I was messing with one of the arms and the arm sort of came apart at the shoulder, and seems loose.

My other gunpla, a Char Zaku... I think it's a lower grade kit, it was only $18... also has a loose hand on it.

How do you deal with loose parts like this? I was thinking about gluing but don't want to mess up my mecha.